This invention relates to pilot cell drive electronics for plasma display panels. The A.C. (alternative current) plasma display capacitive memory panel is well-known in the display technology art at this time. Plasma display pilot cell techniques for such panels are also well-known. This invention relates in particular to a pilot cell drive system having three output states, particularly, a high, pull-up state, a low, pull-down state, and a relaxation, floating state which allows the achievement of a pilot cell electrode voltage which is not directly supplied by an external voltage source.
In the prior art, pilot cells have been fired coincident with the write pulse to achieve photon conditioning and provide for reliable writing of isolated display cells. Pilot cells have been operated in the bistable mode and in some cases have had additional write pulses applied to them to initiate pilot cell discharges and to maintain the lighted condition of pilot cells following a bulk erase operation or other disturbing condition in the operation of the display panel. The system described in this application presents all of these operational features. The present invention provides for a simple pull-up/pull-down pilot cell driver rather than a comparatively complex, multistate pilot cell driver. Additional pilot cell writing pulse voltages for rewriting of pilot cells is derived from the opposite axis sustain drive voltage through a feedback or coupling network. The operation of the pilot cell driver is as a result of allowing the output of the pilot cell driver to float during a portion of the pilot cell drive cycle and controlling the feedback of the sustain voltage so that the appropriate rewrite pulse amplitude is achieved.
Known to applicant and related to the present invention are three pertinent prior art patents. The first patent is U.S. Pat. No. 3,750,159 issued July 31, 1973 and entitled, "Bulk Erase System for Gas Discharge Display Panels." In this patent, a bulk erase operation in the display panel automatically erases all pilot cells because the pilot cells are operating in a sustaining mode just as are all of the display panel visible elements. The pilot cell write drivers float on the sustain driver output and each pilot cell write driver is capable of supplying a full write amplitude pulse. Following a bulk erase the pilot write drivers rewrite the pilot elements. This patent does not anticipate the present invention. The present invention does not use a pilot cell write driver floating on a sustain driver output. The patent does not use feedback from the opposite axis sustain driver to provide the rewrite voltage.
Another pertinent patent known to applicant is U.S. Pat. No. 3,786,484 issued Jan. 15, 1974 and entitled, "Border Control System for Gas Discharge Display Panels." This patent shows border elements, otherwise called pilot cells, operating in a sustain voltage range and capable of being written at a selected time by increasing the direct current supply voltage input to the border sustainer. This patent does not anticipate the present invention because it shows the use of multiple voltages being generated by the pilot cell drive system.
The third pertinent patent known to applicant is U.S. Pat. No. 3,879,634 issued Apr. 22, 1975 and entitled, "Manufacture and Operation of Gas Discharge Panel." This patent shows the use of pilot cells in a plasma display panel and describes the use of such cells to maintain photon conditioning of a plasma display panel. This patent does not anticipate the present system of using a separate pilot cell driver according to the disclosure of this application.
Applicant's earlier U.S. Pat. No's. 4,077,033 issued Feb. 28, 1978 and 4,091,309 issued May 23, 1978 contain additional background information relating to the subject of A.C. plasma display technology. The disclosure of these patents is hereby incorporated in this application by reference.